Ibaraki University and others elucidate structure and function of extracellular polysaccharides produced by edible algae

A research group consisting of Professor Munehiko Asayama from the College of Agriculture at Ibaraki University, BioX Chemical Industries Co., Ltd. (Hiroshima City), and Daiwa Pharmaceutical Co., Ltd. (Setagaya City, Tokyo Prefecture) announced that they have elucidated the composition, structure, and multifunctional properties of extracellular polysaccharides (bxEPS) produced by the edible green alga Parachlorella BX1.5. The bxEPS demonstrated high stability against cations, making it promising as a cosmetic material, and the researchers also confirmed functions including antioxidant, anti-hypertensive, and anti-gray hair effects. Hair growth effects were also confirmed in mice through transdermal administration. Applications are expected in cosmetics and pharmaceutical materials. The results were published in Carbohydrate Polymers on August 25.

The development of "biorefinery technology" utilizing renewable biological resources such as plants and microalgae is attracting global attention. Microalgae possess carbon fixation capabilities, and grow rapidly through photosynthesis, making them promising as next generation biorefinery resources.

Although extracellular polysaccharides (EPS) secreted by microalgae were expected to have applications in health foods, pharmaceuticals, and cosmetics based on their structure and function, basic knowledge regarding the safety of the algae themselves was limited. Therefore, in this study, the patented BX1.5 strain of the edible green alga Parachlorella, which has excellent growth and production of useful substances and has been successfully produced through large-scale outdoor cultivation, was efficiently grown in a nitrogen-depleted medium at low cost and in a short time, and its structure and function were evaluated. Analyses of monosaccharide composition, molecular structure, and chemical properties, and functional evaluation were also conducted.

As a result, bxEPS was identified as a high-molecular-weight acidic rhamnan containing rhamnose, xylose, and glucuronic acid as its main components and lacking sulfate groups, distinguishing it from rhamnan sulfate produced by similar green algae such as Monostroma. Furthermore, its aqueous solution is less reactive with cations and can maintain high viscosity, making it promising for cosmetic applications.

In vitro tests demonstrated physiological activities including antioxidant activity, ACE inhibitory activity (anti-hypertensive effect), and tyrosinase activity enhancement (gray hair prevention).

Furthermore, application of a 0.2% concentration bxEPS aqueous solution to mouse skin confirmed hair follicle enlargement and significant hair growth effects, suggesting potential applications as a hair growth agent.

Asayama commented: "This research systematically elucidated for the first time the structure and function of extracellular polysaccharides produced by the edible microalga Parachlorella, and represents important findings demonstrating application potential in the food, health, and medical fields. Although we underwent extensive trial and error in algae cultivation, polysaccharide purification, and functional analysis, the knowledge gained through this process is extremely valuable. Going forward, we will further investigate the diverse physiological functions of this polysaccharide and develop research through industry-academia collaboration aimed at its social implementation as a sustainable biomaterial."

Journal Information
Publication: Carbohydrate Polymers
Title: Composition, structural features, and multifunctional properties of extracellular polysaccharides from the non-toxic green alga Parachlorella sp.
DOI: 10.1016/j.carbpol.2025.123996